Mobile telephone, apparatus, method and computer implementable instructions product

ABSTRACT

A communication system ( 100 ) is disclosed which uses system frames of a first and a second type. In a system frame of the first type communication with a mobile telephone ( 3 ) is subject to a restriction and in a system frame of the second type communication with said mobile telephone ( 3 ) is not subject to said restriction. It is determined whether or not to communicate with said mobile telephone ( 3 ), in a current system frame, in dependence on whether the current system frame is a first type of system frame or a second type of system frame.

TECHNICAL FIELD

The present invention relates to a communication system and tocomponents thereof for transmitting paging messages to mobile or fixedcommunication devices. The invention has particular, but not exclusive,relevance to paging user equipment employing discontinuous reception inLong Term Evolution (LTE) Advanced systems as currently defined inassociated 3rd Generation Partnership Project (3GPP) standardsdocumentation.

BACKGROUND ART

In communication systems operating according to the LTE Advancedstandards, a radio access network (RAN) provides User Equipment (UE),such as mobile telephones, access to a core network (and hence to otheruser equipment or other network nodes) via one or more of its cells. Aradio access network typically comprises a plurality of base stations(eNB), each of which operates one or more cells of that RAN.Communication between the mobile telephones and the radio access networkis controlled using a Radio Resource Control (RRC) protocol as definedin 3GPP TS 25.331 for UTRAN and TS36.331 for E-UTRAN. RRC handles thecontrol plane signalling of Layer 3 between mobile telephones and theradio access network, and includes, inter alia, functions forbroadcasting system information, paging, connection establishment andrelease, radio bearer establishment, reconfiguration and release,mobility procedures, and power control.

At any given time, mobile telephones may operate either in an ‘RRC idlemode’ or an ‘RRC connected mode’, the latter of which includes a‘CELL_PCH’ (Cell Paging channel) and a ‘URA_PCH’ (URA Paging channel)modes, a ‘CELL_FACH’ (Forward access channel) mode, and a ‘CELL_DCH’(Dedicated Channel) mode for the UTRAN access.

The radio access network controls the transition between the variousoperating modes for each mobile telephone within the cells of its basestations. Since the setting up and termination of an RRC connectionbetween a base station of the RAN and the mobile telephone requiresexchanging of signalling messages and hence utilises valuable systemresources, and also takes some time to complete, the transition fromconnected to idle mode is only allowed under specific circumstances asdefined in the 3GPP TS 25.331 for UTRAN and TS36.331 for E-UTRANstandards, the contents of which are incorporated herein by reference.For example, the serving base station (eNodeB/eNB for E-UTRAN and NodeBfor UTRAN) might instruct a mobile telephone to enter the RRC idle modeonly after it has confirmed that there is no more data to be transmittedto/from the particular mobile telephone (e.g. both uplink and downlinkbuffers are empty).

In particular, RRC protocol provides inactivity timers to controltransitions to lower energy consuming states (i.e. when no data istransmitted within a certain time period), thereby preserving batterylife of the mobile telephones whenever possible whilst also ensuringthat the transition to idle mode does not happen too soon. In UTRAN forexample, a so-called ‘T1’ timer controls the mobile telephone'stransition from DCH to FACH mode, a ‘T2’ timer controls transition fromFACH to PCH mode, and a ‘T3’ timer controls transition from PCH to idlemode. Different inactivity timer values can be set and broadcast by theradio access network, which result in different overall energyconsumption of the mobile telephones (both active and idle) served bythe base stations of that RAN.

For mobile telephones operating in the RRC connected mode, the RAN (e.g.a base station in case of GSM EDGE RAN (GERAN), a Radio NetworkController (RNC) in case of UTRAN, or an eNB in case of E-UTRAN) mayoptimise power consumption by configuring a so-called DiscontinuousReception (DRX) and/or Discontinuous Transmission (DTX) operation. Bothtechniques are based on reducing the mobile telephone's transceiver dutycycle while in active operation.

In DRX mode, the RAN sets a cycle during which the mobile telephone isoperational for a certain period of time and the RAN transmits allscheduling and paging information (for this mobile telephone) duringthis period only. The mobile telephone can thus turn off its transceiverfor the rest of the DRX cycle. DRX also applies to the RRC idle modewith a longer cycle time than in connected mode.

In DTX mode, the mobile telephone does not turn off its transceivercompletely, but keeps monitoring the Physical Downlink Control Channel(PDCCH) to be able to receive data from the base station without unduedelay.

The longer the ‘off’ duration relative to the duty cycle, the more powersaving can be achieved.

A so-called System Frame (SF) is the largest time interval within theframe structure of UTRAN and E-UTRAN which can be used forsynchronization between the RAN and the mobile telephone. Each radioframe within the SF is associated with a ‘relative’ frame number from #0to # n−1 (where ‘n’ is the number of frames in the SF). This radio framenumber (or frame index) is also referred to as System Frame Number(SFN). In E-UTRAN and UTRAN networks, a DRX cycle can be scheduled basedon the SFN of the UTRAN Paging Indication Channel (PICH) or the E-UTRANPhysical Downlink Control Channel (PDCCH).

In the current 3GPP specifications the maximum length of the DRX cycleis less than the length of the SF, as it is limited to 5.12 s and 2.56 sfor UTRAN and E-UTRAN, respectively. When a node in the RAN (e.g. basestation, NodeB, eNB, etc.) needs to send a paging message to the mobiletelephone, it calculates the timing of the paging message (i.e. theradio frame or sub-frame in which the paging message is to be sent) forthe target mobile telephone by taking into account, amongst otherthings, the DRX cycle length currently applied for that mobiletelephone. Paging messages are sent only in those radio frames in whichthe mobile telephone is known to operate its transceiver, in accordancewith its DRX cycle.

SUMMARY OF INVENTION Technical Problem

More recently, notwithstanding the currently specified maximum values,longer maximum lengths of the DRX cycle have been proposed which mayexceed the SF length. Scheduling a DRX cycle using a length of the DRXcycle that is longer than the length of the SF, however, can hinder theeffectiveness of the DRX functionality.

For example, a particular problem arises if the mobile telephone isconfigured with a DRX cycle that exceeds the SF length for that type ofRAN (which is currently 40.96 s for UTRAN and 10.24 s for E-UTRAN) thatthe mobile telephone might not be able to benefit from all the potentialreductions in its power consumption. Further, in some cases, the mobiletelephone's transceiver might operate out of sync with the pagingmessages transmitted by the RAN for this mobile telephone, which canresult in the mobile telephone listening to paging messages in thecorrect radio frame, but in the wrong system frame.

For example, the above problems may arise when (in accordance withsection 7.1.3.1 of TR23.887) an idle mode mobile telephone is configuredwith an ‘extended’ DRX cycle (i.e. a DRX cycle exceeding the length ofthe SF) for the given RAN, in order to achieve further reductions in themobile telephone's battery consumption (compared to e.g. using anon-extended DRX cycle). In this case however, if the mobile telephoneis configured with an extended DRX cycle that is longer than the SF usedin that type of RAN (for example a DRX cycle that is twice the SFduration) and paging for this mobile telephone is scheduled in a singleframe of its DRX cycle (for example at SFN #512 of every second systemframe), the mobile telephone would have to turn on its transceiver ateach frame corresponding to that SFN index in every SF (in this example,each frame number #512) because it cannot distinguish between the samenumbered frames of consecutive system frames. This is wasteful of thebattery usage of the mobile telephone. Although this problem is not asserious when the DRX cycle is only twice the SF length, the longer theDRX cycle (i.e. the longer the mobile telephone's transceiver isintended to remain off), the more wasteful of the mobile telephone'sbattery consumption this approach becomes.

On the other hand, if the mobile telephone tries to maximise its powersavings by not turning on its transceiver in each radio frame having anSFN index common with the SFN index for paging, then there is a riskthat some or all of the paging messages will not be received by thismobile telephone, especially when the mobile telephone and the RAN donot count the first SF of the applicable DRX cycle from the same SF (themobile telephone and RAN being out of sync).

Therefore, using the current techniques, it is not possible to optimisepower savings and at the same time minimise failure of reception ofsystem messages by the mobile telephone.

The present invention aims to provide an improved communication systemand improved components thereof which overcome or at least alleviate oneor more of the above issues.

Solution to Problem

In one aspect, the invention provides a mobile telephone forcommunicating with a network entity in a communication system which usesa plurality of system frames wherein each system frame is subdivided inthe time domain into a plurality of radio frames, the mobile telephonecomprising: means for receiving at least one signalling messageindicative of a communication being initiated for said mobile telephone;means for determining whether a current system frame is a first type ofsystem frame in which communication with said mobile telephone issubject to a restriction or a second type of system frame in whichcommunication with said mobile telephone is not subject to saidrestriction; means for determining whether or not to listen for acommunication from said network entity, in said current system frame, independence on whether the current system frame is determined to be afirst type of system frame or a second type of system frame; and meansfor listening for a communication from said network entity based onwhether or not said determining means determines the current systemframe to be a first type of system frame.

The determining means may be operable to determine that said receivershould not listen for a communication from said network entity in saidfirst type of system frame.

In said second type of system frame communication with said mobiletelephone may be subject to a power saving cycle in which communicationswith said mobile telephone are restricted in at least one radio frame.For example, the power saving cycle may comprise a first period of atleast one radio frame in which communication with said mobile telephoneis restricted and a second period of at least one radio frame in whichcommunication with said mobile telephone is allowed.

The first type of system frame may be a dormant system frame or awake-up system frame and the second type of system frame may be anactive system frame.

The listening means may be operable to listen for a communication fromsaid network entity for the duration of said second period of at leastone radio frame. The listening means may be operable to listen forpaging and/or system information messages in said second type of systemframe.

In one possibility, the mobile telephone may further comprise means forobtaining information identifying a base system frame and informationidentifying at least one of a first set of system frames of the firsttype and a second set of system frames of the second type, and thedetermining means may be operable to determine said current system frameto be said first type of system frame or to be said second type ofsystem frame in dependence on said information identifying said basesystem frame and said information identifying said at least one of saidfirst and second set of system frames. In this case, for example, thebase system frame may comprise a first system frame of said first orsaid second set of system frames, wherein said first and said second setof system claims follow each other in a cyclical manner, and whereinsaid determining means may also be operable to determine said currentsystem frame to be included in said first or in said second set ofsystem frames.

The mobile telephone may further comprise means for providing to anetwork apparatus information relating to a capability of said mobiletelephone to communicate using said first and/or said second type ofsystem frame.

The mobile telephone may further comprise means for providing to anetwork apparatus information relating to said number of said first typeof system frames and/or information relating to said number of saidsecond type of system frames to be used in communication with saidmobile telephone. In this case, the providing means may be operable toprovide to said network apparatus said information identifying said atleast one of said first and second set of system frames. For example,the providing means may be operable to generate and send at least onemessage to a core network entity and to include said information in saidat least one message. The at least one message may comprise a non-accessstratum (NAS) message. For example, the at least one message maycomprise at least one of an Attach message, a Routing Area Update (RAU)message, and a Tracking Area Update (TAU) message.

The mobile telephone may further comprise means for obtaininginformation relating to a capability of said network entity tocommunicate with said mobile telephone using said first and/or saidsecond type of system frames. In this case, the capability informationobtaining means may be operable to obtain said network capabilityinformation from a system information message and/or from a non-accessstratum (NAS) message.

The capability information may comprise information relating tocompatibility with a power saving cycle (for example, an extendeddiscontinuous reception cycle).

The mobile telephone may further comprise means for obtainingconfiguration information relating to said first and second set ofsystem frames. In this case, the configuration information obtainingmeans may be operable to obtain said first and second set of systemframes from an Open Mobile Alliance (OMA) device management (DM) entity.For example, the configuration information obtaining means may beoperable to receive at least one message from said OMA DM entity, saidat least one message comprising said first and second set of systemframes.

In another aspect, the invention provides an apparatus for schedulingcommunications between a mobile telephone and a network entity in acommunication system which uses a plurality of system frames whereineach system frame is subdivided in the time domain into a plurality ofradio frames, the apparatus comprising: means for determining whether acurrent system frame is a first type of system frame in whichcommunication with said mobile telephone is subject to a restriction ora second type of system frame in which communication with said mobiletelephone is not subject to said restriction; and means for determiningwhether or not to communicate with said mobile telephone, in saidcurrent system frame, in dependence on whether the current system frameis determined to be a first type of system frame or a second type ofsystem frame.

The determining means may be operable to determine that said apparatusshould not communicate with said mobile telephone in said first type ofsystem frame.

In said second type of system frame communication with said mobiletelephone may be subject to a power saving cycle in which communicationswith said mobile telephone are restricted in at least one radio frame.For example, the power saving cycle may comprise a first period of atleast one radio frame in which communication with said mobile telephoneis restricted and a second period of at least one radio frame in whichcommunication with said mobile telephone is allowed.

The apparatus may be operable to communicate with said mobile telephoneduring said second period of at least one radio frame. For example, theapparatus may be operable to send paging and/or system informationmessages to said mobile telephone during said second period of at leastone radio frame.

The first type of system frame may be a dormant system frame or awake-up system frame and the second type of system frame may be anactive system frame.

The apparatus may further comprise means for obtaining informationidentifying a base system frame and information identifying at least oneof a first set of system frames of the first type and a second set ofsystem frames of the second type and said determining means may beoperable to determine said current system frame to be said first type ofsystem frame or to be said second type of system frame in dependence onsaid information identifying said base system frame and said informationidentifying said at least one of said first and second set of systemframes.

The base system frame may comprise a first system frame of said first orsaid second set of system frames, wherein said first and said second setof system claims follow each other in a cyclical manner, and whereinsaid determining means may be operable to determine said current systemframe to be included in said first or in said second set of systemframes.

The apparatus may further comprise means for obtaining from said mobiletelephone information relating to a capability of said mobile telephoneto communicate using said first and/or said second type of system frame.

The apparatus may further comprise means for obtaining from said mobiletelephone said information relating to said number of said first type ofsystem frames and/or said information relating to said number of saidsecond type of system frames to be used in communication with saidmobile telephone. In this case, the obtaining means may be operable toobtain said information identifying said at least one of said first andsecond set of system frames. The obtaining means may be operable toreceive at least one message from said mobile telephone, the at leastone message including said information. In this case, the at least onemessage may comprise a non-access stratum (NAS) message. For example,the at least one message may comprise at least one of an Attach message,a Routing Area Update (RAU) message, and a Tracking Area Update (TAU)message.

The apparatus may further comprise means for providing informationrelating to a capability of said apparatus to communicate with saidmobile telephone using said first and/or said second type of systemframes. In this case, the capability information providing means may beoperable to provide said network capability information by sending atleast one system information message and/or at least one non-accessstratum (NAS) message. The capability information may compriseinformation relating to a compatibility of the apparatus with a powersaving cycle (for example, an extended discontinuous reception cycle).

The apparatus may comprise a radio access network entity. In this case,the radio access network entity may comprise means for sending to saidmobile telephone information relating to said current system frame. Theinformation relating to said current system frame may comprise currenttime information and/or an index identifying said current system frame.The sending means may be operable to broadcast system informationcomprising said information relating to said current system frame.

The apparatus may further comprise means for paging said mobiletelephone. The paging means may be operable to page said mobiletelephone upon receipt of a request from another entity. The pagingmeans may be operable to page said mobile telephone in dependence onwhether the current system frame is determined to be a first type ofsystem frame or a second type of system frame. The paging means may beoperable to send a predetermined number of paging messages to saidmobile telephone.

The radio access network entity may further comprise means forproviding, to a core network entity, information identifying a time whena message from said core network entity was sent by said radio accessnetwork entity to said mobile telephone.

The radio access network entity may comprise at least one of a basestation and a radio network controller.

The apparatus may comprise a core network entity. In this case, the corenetwork entity may comprise means for detecting a trigger for pagingsaid mobile telephone. The core network entity may be operable toinitiate paging of said mobile telephone upon said detecting meansdetecting said trigger for paging said mobile telephone. For example,the trigger may comprise a new communication being initiated for saidmobile telephone.

The core network entity may be operable to request at least one radioaccess network entity to page said mobile telephone during a systemframe of said first type. For example, the core network entity may beoperable to request said at least one radio access network entity topage said mobile telephone by sending a paging request to said at leastone radio access network entity during a system frame of the first type.The core network entity may also be operable to request said at leastone radio access network entity to page said mobile telephone bysending, to each of said at least one radio access network entity,information identifying said at least one of said first and second setof system frames and information for identifying which one of saidplurality of system frames is a system frame of the first and secondtype.

The information identifying which one of said plurality of system framesis a system frame of the first and second type may comprise a systemframe index. The information identifying which one of said plurality ofsystem frames is a system frame of the first and second type maycomprise a time value.

In another aspect, the invention provides a mobile telephone forcommunicating with a network entity in a communication system which usesa plurality of system frames wherein each system frame comprises aplurality of radio frames, the mobile telephone comprising a processorand transceiver, wherein: the processor is configured to i) determinewhether a current system frame is a first type of system frame in whichcommunication with said mobile telephone is subject to a restriction ora second type of system frame in which communication with said mobiletelephone is not subject to said restriction; and ii) determine whetheror not to listen for a communication from said network entity, in saidcurrent system frame, in dependence on whether the current system frameis determined to be a first type of system frame or a second type ofsystem frame; and the transceiver is configured to listen for acommunication from said network entity when it is determined that thecurrent system frame is a first type of system frame.

In another aspect, the invention provides an apparatus for schedulingcommunications between a mobile telephone and a network entity in acommunication system which uses a plurality of system frames whereineach system frame comprises a plurality of radio frames, the apparatuscomprising: a processor configured to i) determine whether a currentsystem frame is a first type of system frame in which communication withsaid mobile telephone is subject to a restriction or a second type ofsystem frame in which communication with said mobile telephone is notsubject to said restriction; and ii) determine whether or not tocommunicate with said mobile telephone, in said current system frame, independence on whether the current system frame is determined to be afirst type of system frame or a second type of system frame.

In another aspect, the invention provides a method performed by a mobiletelephone for communicating with a network entity in a communicationsystem which uses a plurality of system frames wherein each system frameis subdivided in the time domain into a plurality of radio frames, themethod comprising: determining whether a current system frame is a firsttype of system frame in which communication with said mobile telephoneis subject to a restriction or a second type of system frame in whichcommunication with said mobile telephone is not subject to saidrestriction; determining whether or not to listen for a communicationfrom said network entity, in said current system frame, in dependence onwhether the current system frame is determined to be a first type ofsystem frame or a second type of system frame; and listening for acommunication from said network entity when it is determined that thecurrent system frame is a first type of system frame.

In another aspect, the invention provides a method performed by anapparatus for scheduling communications between a mobile telephone and anetwork entity in a communication system which uses a plurality ofsystem frames wherein each system frame is subdivided in the time domaininto a plurality of radio frames, the method comprising: determiningwhether a current system frame is a first type of system frame in whichcommunication with said mobile telephone is subject to a restriction ora second type of system frame in which communication with said mobiletelephone is not subject to said restriction; and determining whether ornot to communicate with said mobile telephone, in said current systemframe, in dependence on whether the current system frame is determinedto be a first type of system frame or a second type of system frame.

Aspects of the invention extend to computer program products such ascomputer readable storage media having instructions stored thereon whichare operable to program a programmable processor to carry out a methodas described in the aspects and possibilities set out above or recitedin the claims and/or to program a suitably adapted computer to providethe apparatus recited in any of the claims.

Advantageous Effects of Invention

According to the present invention, it is possible to provide animproved communication system and improved components which optimisespower savings and at the same time minimises failure of reception ofsystem messages by the mobile telephone.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 schematically illustrates a mobile telecommunication system towhich embodiments of the invention may be applied;

FIG. 2a illustrates a generic frame structure defined for use in the LTEcommunication network;

FIG. 2b illustrates the way in which a slot illustrated in FIG. 2a isformed of a number of time-frequency resources;

FIG. 3 is a block diagram illustrating the main components of the mobiletelephone forming part of the system shown in FIG. 1;

FIG. 4 is a block diagram illustrating the main components of a basestation forming part of the system shown in FIG. 1;

FIG. 5 shows an example timing diagram illustrating a method performedby components of the communication system when transmitting pagingmessages to a mobile telephone employing an extended DRX cycle;

FIG. 6 shows an example timing diagram illustrating a modification ofthe method shown in FIG. 5;

FIG. 7 shows an example timing diagram illustrating another methodperformed by components of the communication system when transmittingpaging messages to a mobile telephone employing an extended DRX cycle;

FIG. 8 shows an example timing diagram illustrating yet another methodperformed by components of the communication system when transmittingpaging messages to a mobile telephone employing an extended DRX cycle;

FIG. 9 shows an example timing diagram illustrating a method performedby components of the communication system when configuring an extendedDRX cycle for a mobile telephone forming part of the system shown inFIG. 1;

FIG. 10a illustrates an exemplary extended DRX cycle applicable to theLTE frame structure for E-UTRAN;

FIG. 10b illustrates an exemplary method for calculating scheduling ofactive and dormant system frames in E-UTRAN;

FIG. 10c illustrates another exemplary method for calculating schedulingof active and dormant system frames using sequential numbers assigned toeach system frame;

FIG. 11a illustrates an exemplary method for calculating a base systemframe by the mobile telephone using the current time and current systemframe number and a time parameter related to the base system frameprovided by the core network,

FIG. 11b illustrates an exemplary configuration of an extended DRX cycleaccording to the invention;

FIG. 11c illustrates a modification of the exemplary method of FIG. 6;

FIG. 12a illustrates additional details of the exemplary method of FIG.8; and

FIG. 12b illustrates a modified extended DRX cycle including wake-upsystem frames.

DESCRIPTION OF EMBODIMENTS

Overview

FIG. 1 schematically illustrates a mobile (cellular) telecommunicationsystem 1 that includes user equipment, e.g. mobile telephones 3-1 to 3-3and a number of base stations 5-1 to 5-3. Each of the base stations 3shown in FIG. 1 belongs to a different radio access network RAN-A toRAN-C, respectively, and each radio access network shown includes onlyone base station for the sake of simplicity. However, it will beappreciated that in a deployed system each radio access networktypically comprises other base stations as well and/or any of the basestations may belong to more than one radio access network. Similarly,although three mobile telephones 3 are shown in FIG. 1 for the sake ofsimplicity, it will be appreciated that many more mobile telephones 3can be provided in a deployed system.

In this system, each base station 5 is coupled to a core network 7 thatincludes, amongst other, a Mobility Management Entity (MME) 9 thatmanages the mobility of mobile telephones 3 within the network, and aHome Subscriber Server (HSS) 11 which stores and enforces usersubscription related configuration. The system also includes a so-calledOpen Mobile Alliance (OMA) Device Management (DM) server 12 forconfiguring various operating parameters of the mobile telephones 3 (viathe core network 7 and the RANs).

The core network 7 is also coupled to other networks, such as theInternet (not shown). Using this network architecture, the mobiletelephone 3 can access the core network 7 and/or the Internet via one ormore of the cells operated by the base stations 5-1 to 5-3.

In this system, each radio access network supports DRX functionality asdefined in the relevant 3GPP specifications discussed above. However,the core network 7 and possibly some of the RANs also support aso-called ‘Extended DRX’ functionality. This Extended DRX (or ‘E-DRX’)functionality beneficially allows the network to apply a DRX cycle, fora given mobile telephone 3, which is longer in duration than the maximumlength of the system frame defined for that type of radio access networkwhilst ensuring appropriate synchronisation of the DRX cycle in order tomaximise power savings and ensure that the mobile telephone 3 listens inappropriate radio frames for paging messages or the like.

As specified in section 10.5.5.6 of 3GPP TS24.008, the contents of whichare incorporated herein by reference, a mobile telephone 3 is requiredto notify the RAN (via a core network element such as an SGSN, an MME,etc.) about its current (core network specific) DRX cycle length (ifapplicable) in a so-called ‘DRX parameter’ information element (IE). TheDRX specific values that may be used in accordance with the currentversion of TS24.008 are illustrated in Table 1 below.

A mobile telephone 3 configured with a DRX functionality may provide theDRX parameter TE to the core network 7 during a location registrationprocedure (e.g. in an ‘Attach’ request, a ‘Routing Area Update’ (RAU)request, or a ‘Tracking Area Update’ (TAU) request sent to a corenetwork entity). When a subsequent trigger for paging the mobiletelephone 3 (such as downlink data transfer from inside/outside thenetwork) occurs, the core network 7 informs the RAN(s) about the targetmobile telephone's 3 relevant DRX parameters and identifier (e.g. themobile telephone's 3 International Mobile Subscriber Identifier or‘IMSI’) thereby instructing the appropriate RAN(s) to carry out pagingof the mobile telephone 3 according to the applicable DRX configuration.The RAN(s) can thus calculate paging timing for the target mobiletelephone 3 from the received DRX parameter and IMSI and send one ormore paging message(s) to the mobile telephone 3 at the calculated time(i.e. in radio frame(s) in which the transceiver of that particularmobile telephone 3 is expected to be active). Further details of the DRXscheduling are defined in section 7.1 of 3GPP TS36.304 for E-UTRAN andin section 8.3 of 3GPP TS25.304 for UTRAN, the contents of which areincorporated herein by reference.

3GPP TR23.887 describes possible solutions for UE power consumptionoptimisation. In section 7.1.3.1 of TR23.887 an ‘extended’ DRX cycle(i.e. exceeding the length of the SF) is suggested for the UTRAN/E-UTRANin idle mode, which can be configured by using one of the newly definedDRX cycle length values in the DRX parameter IE. The suggested valuesfor this extended DRX cycle are illustrated in Table 2 below.

TABLE 1 DRX cycle lengths previously defined in TS24.008 bits UTRANE-UTRAN 8 7 6 5 lu and S1 mode specific DRX (sec) DRX (sec) 0 0 0 0 Forlu mode, CN Specific DRX cycle length coefficient not specified by theUE, i.e. the system information value ‘CN domain specific DRX cyclelength’ is used. For S1 mode, DRX value not specified by the UE. 0 1 1 0CN Specific DRX cycle 0.64 0.32 length coefficient 6 and T = 32 0 1 1 1CN Specific DRX cycle 1.28 0.64 length coefficient 7 and T = 64 1 0 0 0CN Specific DRX cycle 2.56 1.28 length coefficient 8 and T = 128 1 0 0 1CN Specific DRX cycle 5.12 2.56 length coefficient 9 and T = 256

TABLE 2 Extended DRX cycle lengths in accordance with TR23.887 bitsUTRAN E-UTRAN 8 7 6 5 lu and S1 mode specific DRX (sec) DRX (sec) 1 0 10 CN Specific DRX cycle 10.24 5.12 length coefficient 10 and T = 512 1 01 1 CN Specific DRX cycle 20.48 10.24 length coefficient 11 and T = 10241 1 0 0 CN Specific DRX cycle 40.96 20.48 length coefficient 12 and T =2048 1 1 0 1 CN Specific DRX cycle 81.92 40.96 length coefficient 13 andT = 4096 1 1 1 0 CN Specific DRX cycle 163.84 81.92 length coefficient14 and T = 8192 1 1 1 1 CN Specific DRX cycle 327.68 163.84 lengthcoefficient 15 and T = 16384

In the system illustrated in FIG. 1, the mobile telephone 3 and thenetwork (i.e. the core network 7/the RAN serving the mobile telephone 3)also support DRX cycles longer than the SF length applicable for thattype of RAN. In this embodiment however, the way in which this isfacilitated is enhanced by way of so-called ‘dormant’ system frames inwhich no communications are to be scheduled and ‘active’ system framesin which communications may be scheduled.

The mobile telephone 3 and the network (i.e. an entity in the corenetwork 7 and/or the RAN serving the mobile telephone 3) communicatewith one another to configure a DRX cycle to be used for communicationswith that mobile telephone 3 and to specify how many dormant SFs and howmany active SFs will be used in communications with that mobiletelephone 3 and/or in which order the dormant and active SFs will followeach other. In order to ensure that the mobile telephone 3 and thenetwork remain synchronised during the extended DRX cycle, the mobiletelephone 3 and the network exchange with each other informationidentifying at least the first SF of the DRX cycle for the mobiletelephone 3. The dormant and active SFs are thus UE specific and can beconfigured by/for each mobile telephone 3 as needed (e.g. in dependenceon the level of power optimisation needed for a particular mobiletelephone 3).

In this system, the mobile telephone 3 is configured to activate itstransceiver, in any active SFs, according to normal DRX schedulingmethods defined in the current 3GPP specification for non-extended DRXcycles (i.e. DRX cycles that do not exceed the length of the systemframe). However, the mobile telephone 3 is configured to switch off itsreceiver (and hence not listen for any paging messages) for the durationof each dormant SF. In other words, although the DRX cycle extends overmultiple system frames, communication between the network and the mobiletelephone 3 is restricted to some of the system frames only. Thus anysystem frames in which no communication is expected/scheduled can beclassified as dormant SFs whereas any system frames in whichcommunication is expected/can be scheduled can be classified as activeSFs (even if actual communication does not actually take place is suchactive system frames between the network and the mobile telephone 3).

Since the network is also aware of the current DRX configuration for themobile telephone 3 and also controls/keeps track of its currentoperational mode (e.g. ‘RRC active’/‘RRC idle’), the network isbeneficially able to schedule any paging messages during active SFs andto avoid scheduling any paging messages (or any other communications)for the mobile telephone 3 during dormant SFs. This approachbeneficially improves the power conservation capabilities of the mobiletelephone 3 operating in a DRX mode without hindering the successfuldelivery of paging/signalling messages to the mobile telephone 3 (e.g.due to the mobile telephone 3 and the network being out of sync duringtheir respective DRX cycles).

This way, it is possible to configure various kinds of extended DRXcycles for the mobile telephone 3 by simply selecting the appropriatenumber (and order) of active and dormant system frames for the desiredDRX cycle. Once the DRX functionality is activated for the mobiletelephone 3, a set of one or more active SFs will follow a set of one ormore dormant SFs in the specified configuration and in a cyclical manneruntil the DRX cycle is reconfigured or the mobile telephone 3 moves to adifferent RAN.

In the following, the use of extended DRX cycles based on a combinationof active and dormant SFs are referred to as the extended DRX featureand the procedure in which the mobile telephone 3 switches off itsreceiver for the duration of any dormant SFs and performs normal DRXprocedures according to the current (non-extended) DRX methods duringactive SFs is referred to as the extended DRX procedure.

By way of an example scenario in the system shown in FIG. 1, furtherdetails of the extended DRX feature and related procedures are givenbelow.

In this particular example, the mobile telephone 3-2 is being served byRAN-B (which supports extended DRX cycles). Initially, the mobiletelephone 3-2 registers its location with the core network 7 byperforming an appropriate RAU/TAU procedure upon the mobile telephone3-2 entering a cell of the base station 5-2. During this procedure, themobile telephone 3-2 also provides its DRX configuration to the RAN-B(e.g. to the base station 5-2 or another node of RAN-B) by including aDRX parameter IE in a message sent to the core network 7. The DRXconfiguration may be provided to the RAN-B either directly, or via thecore network 7, e.g. as part of the above RAU/TAU procedure.

During the RAU/TAU procedure the core network 7 provides an indicationto the mobile telephone 3 to identify the first SF of the extended DRXcycle (which, in this example, is also the first active SF of the set ofone or more active SFs) to ensure that the mobile telephone 3 and thenetwork remain in sync with each other. This indication may be, forexample, a time value and/or another identification of the system framerepresenting a first SF of the mobile telephone's 3-2 extended DRX cycleat least whilst the mobile telephone 3-2 is being served via the currentRAN(s), in this case RAN-B. Of course, as its name implies, the DRXcycle is cyclical, thus there are more than one ‘first system frame’that can be indicated to the mobile telephone 3-2. However, regardlessof which ‘first SF’ is indicated, the mobile telephone 3-2 can alwayswork out the first SF of the current DRX round (since the length of oneround of the extended DRX cycle is known).

When the mobile telephone 3-2 enters into an RRC idle mode (i.e. whenits ‘T3’ timer configured by the RAN-B expires) whilst attached to theRAN-B, it invokes an extended DRX cycle as specified in its DRXconfiguration and using the indication provided by the core network 7identifying the first SF of this extended DRX cycle. Of course, it willalso be appreciated that the extended DRX cycle might be invoked byother means, i.e. regardless of the RRC mode of the mobile telephone3-2.

When the core network 7 detects a trigger for paging the mobiletelephone 3-2 (e.g. an incoming call, a request for a downlink datatransfer, or the like), it requests the RAN-B currently serving thismobile telephone 3-2 to carry out paging of the mobile telephone 3-2.The core network 7 also provides the mobile telephone's 3-2 DRXconfiguration to the RAN-B (if it hasn't been provided yet) and the TMSIassociated with the mobile telephone 3-2 so that the RAN-B can schedulethe paging messages accordingly (i.e. to the right mobile telephone 3-2and at the right time).

In this particular example, the RAN-B will determine, from the status ofthe mobile telephone 3-2, the relevant DRX configuration information andIMSI available to it that the mobile telephone 3-2 is configured with anextended DRX cycle. Therefore, before sending any paging messages, theRAN-B (e.g. base station 5-2 serving the mobile telephone 3-2) checkswhether the current system frame is an active SF or a dormant SF forthis particular mobile telephone 3-2. If the RAN-B determines that thecurrent system frame is an active SF for this mobile telephone 3-2, itschedules a paging message in the appropriate radio frame of the currentsystem frame and thus alerts the mobile telephone 3-2 about the newcommunication being initiated for the mobile telephone 3-2. In order tominimise loss or incorrect reception of the paging message, the pagingmessage may be re-sent for a predetermined (operator specific) number oftimes during the same or subsequent active system frame(s) at leastuntil the mobile telephone 3-2 confirms receipt of the paging message(either explicitly or implicitly).

On the other hand, if the RAN-B determines that the current system frameis a dormant SF for this mobile telephone 3-2, it does not schedule(i.e. delays transmission of) any paging messages until the next activeSF for this mobile telephone 3-2.

This approach beneficially provides a flexible, extended DRX cyclesolution that results in improved battery life of the mobile telephonewithout compromising on its ability to receive paging messages (andother system updates) without unnecessary delay.

LTE Frame Structure

Before discussing the specific ways in which embodiments of theinvention can be implemented, a brief description will be given of theaccess scheme and a general frame structure agreed for LTEcommunications. An Orthogonal Frequency Division Multiple Access (OFDMA)technique is used for the downlink to allow the mobile telephone 3 toreceive data over the air interface with the base station 5. Differentsub-carriers are allocated by the base station 5 (for a predeterminedamount of time) to the mobile telephone 3 depending on the amount ofdata to be sent to the mobile telephone 3. These blocks of sub-carriersare referred to as physical resource blocks (PRBs) in the LTEspecifications. PRBs thus have a time and frequency dimension. The basestation 5 dynamically allocates PRBs for each device that it is servingand signals the allocations for each radio frame to each of thescheduled devices in a control channel.

FIG. 2a illustrates one generic frame structure agreed for LTEcommunications over the air interface with the base station 5. As shown,one frame 13 is 10 ms (milliseconds) long and comprises ten sub-frames15 of 1 ms duration (known as a Transmission Time Interval (TTI)). Eachsub-frame or TTI comprises two slots 17 of 0.5 ms duration. Each slot 17comprises either six or seven OFDM symbols 19, depending on whether thenormal or extended cyclic prefix (CP) is employed. The total number ofavailable sub-carriers depends on the overall transmission bandwidth ofthe system. The LTE specifications define parameters for systembandwidths from 1.4 MHz to 20 MHz and one PRB is currently defined tocomprise twelve consecutive subcarriers for one slot 17 (although thiscould clearly be different). The transmitted downlink signal comprisesNBW subcarriers for a duration of Nsymb OFDM symbols. It can berepresented by a resource grid as illustrated in FIG. 2b . Each box inthe grid represents a single sub-carrier for one symbol period and isreferred to as a resource element (RE). As shown, each PRB 21 is formedfrom twelve consecutive sub-carriers and (in this case) seven symbolsfor each subcarrier; although in practice the same allocations are madein the second slot 17 of each sub-frame 15 as well.

As mentioned above, the so-called system frame represents the largesttime interval within the above described frame structure which can beused for synchronisation between the radio access network and the mobiletelephone 3. The length of the system frame is dependent on the type ofaccess network and currently it is defined as 4096 frames 13 (i.e. 40.96seconds) for UTRAN and 1024 frames 13 (i.e. 10.24 seconds) for E-UTRAN.Further details of the frame structure can be found in 3GPP standardsspecification TS25.402 for UTRAN, and TS36.331 and TS36.211 for E-UTRAN,the entire contents of which are incorporated herein by reference.

Mobile Telephone

FIG. 3 is a block diagram illustrating the main components of the mobiletelephone 3 shown in FIG. 1. As shown, the mobile telephone 3 includes atransceiver circuit 31 which transmits signals to, and receives signalsfrom, the base station 5 via antenna 33. Although not necessarily shownin FIG. 3, the mobile telephone 3 may of course have all the usualfunctionality of a conventional mobile telephone 3 (such as a userinterface 35) and this may be provided by any one or any combination ofhardware, software and firmware, as appropriate. Software may bepre-installed in the memory 39 and/or may be downloaded via thetelecommunications network or from a removable data storage device(RMD), for example.

The controller 37 is configured to control overall operation of themobile telephone 3 by, in this example, program instructions or softwareinstructions stored within the memory 39. As shown, these softwareinstructions include, among other things, an operating system 41, acommunications control module 43, a discontinuous reception module 45;and an open mobile alliance device management module 47.

The communications control module 43 controls communication with thebase station 5 including, for example, allocation of resources to beused by the transceiver circuit 31 in its communications with the basestation 5. The communications control module 43 also controlscommunication with the core network 7 (via the base station 5).

The discontinuous reception module 45 controls the discontinuousreception (and/or transmission) operation of the mobile telephone 3,e.g. when the mobile telephone is in idle mode. The discontinuousreception module 45 also provides the configuration of the discontinuousreception of the mobile telephone 3 to the core network 7 (viatransceiver circuit 31) in an appropriately formatted signallingmessage. If the mobile telephone 3 is attached to a RAN which supportsthe extended DRX cycle functionality, the discontinuous reception module45 also keeps track of the active and dormant system frames.

The open mobile alliance device management module 47 is operable tointerface with the OMA DM entity 12 (via the core network 7) forreceiving and storing configuration parameters for the extended DRXcycle functionality of the mobile telephone 3.

Base Station

FIG. 4 is a block diagram illustrating the main components of a basestation 5. The base station 5 is a fixed communications node providingservices to user equipment (e.g. the mobile telephones 3) within itscoverage area (i.e. one or more cells). As shown, the base station 5includes a transceiver circuit 51 which transmits signals to, andreceives signals from, the mobile telephone 3 via at least one antenna53. The base station 5 also transmits signals to and receives signalsfrom the core network 7 via a network interface 55.

The controller 57 is configured to control overall operation of the basestation 5 by, in this example, program instructions or softwareinstructions stored within the memory 59. As shown, these softwareinstructions include, among other things, an operating system 61, acommunications control module 63, a discontinuous transmission module65, and a paging module 67.

The communications control module 63 controls communications between thebase station 5 and the mobile telephones 3, and the network devices suchas the MME 9, the HSS 11, and the OMA DM 12.

The discontinuous transmission module 65 controls the discontinuoustransmission (and reception) of messages between the base station 5 andthe mobile telephones 3 attached thereto. The discontinuous receptionmodule 65 receives the DRX configuration applicable for a particularmobile telephone 3 either directly from that mobile telephone 3 or viathe core network 7. If the base station 5 (i.e. the RAN to which itbelongs) supports the extended DRX cycle functionality, thediscontinuous transmission module 65 also keeps track of the active anddormant system frames for the mobile telephones 3 this base station 5 iscurrently serving.

The paging module 67 performs paging for the mobile telephones 3 in thebase station's 5 coverage area, upon receiving an appropriatelyformatted paging request from the core network 7, in accordance with theDRX configuration (if any) configured for the particular mobiletelephone 3 to be paged.

In the above description, the mobile telephone 3 and the base station 5are described for ease of understanding as having a number of discretemodules (such as the communications control modules and the DRX/DTXmodules). Whilst these modules may be provided in this way for certainapplications, for example where an existing system has been modified toimplement the invention, in other applications, for example in systemsdesigned with the inventive features in mind from the outset, thesemodules may be built into the overall operating system or code and sothese modules may not be discernible as discrete entities. These modulesmay also be implemented in software, hardware, firmware or a mix ofthese.

Operation

A number of different embodiments will now be described that illustratehow different aspects of the invention can be put into effect usingcomponents of the above described system. The embodiments will bedescribed with reference to the timing diagrams shown in FIG. 5 to FIG.8.

First Embodiment—DRX Cycle Synchronisation Using Current TimeInformation

FIG. 5 shows an example timing diagram illustrating a method performedby components of the communication system 1 when carrying out paging ofa mobile telephone 3 configured with an extended DRX cycle.

In this embodiment, the mobile telephone 3 obtains current timeinformation from the respective RAN(s) it is currently using. In thisexample, the current time information is broadcast as part of the SystemInformation (SI) message, as generally shown in steps S501 a and S501 bperformed by (the base stations 5 of) RAN-A and RAN-B, respectively. Thecurrent time information allows the mobile telephone 3 to synchronisethe operation of its modules to the RAN it is using. In this example,the SI message broadcast by RAN-B (at S501 b) also includes an indicator(e.g. an ‘Extended DRX feature support indicator’ flag, IE, or the like)informing the mobile telephone 3 that the RAN-B supports the extendedDRX cycle feature. Therefore, the mobile telephone 3 can be notified byway of the SI broadcast that DRX cycles longer than the applicablesystem frame can be used in the RAN-B, if required.

Using information obtained from the SI broadcast message (e.g. anidentifier of the RAN and/or a cell of a base station 5 forming part ofthe RAN, applicable channel configuration, list of radio technologiessupported by the RAN, etc.), the mobile telephone 3 informs the corenetwork 7 (e.g. the MME 9 or another core network entity) about itscurrent location. In order to do so, the communications control module43 generates and sends (via a base station 5 of its RAN) anappropriately formatted non-access stratum (NAS) message to the corenetwork 7. As shown at step S503, this NAS message may include any one(or more) of an ‘Attach Request’ message, a ‘RAU Request’ message, and a‘TAU Request’ message. The mobile telephone 3 also includes in thismessage information relating to its DRX configuration, for example,parameters specifying the number of active SFs (Na) and the number ofdormant SFs (Nd).

The core network 7 (which also supports the extended DRX feature) candetermine that the mobile telephone 3 supports the extended DRX featurewhen it receives the above parameters (i.e. Ns and Nd). Therefore, thecore network 7 selects a suitable time of base SF (TSFb) for this mobiletelephone 3. The core network can select any point in time as the TSFb,for example, the time of receipt of the Attach/RAU/TAU request messagefrom the mobile telephone 3, the time of sending the Attach/RAU/TAUaccept message, or any arbitrary (past or future) time such as‘2013-01-01 00:00:00.00’.

The core network 7 stores the received Na, Nd parameters and thegenerated TSFb value as the UE specific parameters for the extended DRXfeature with respect to this mobile telephone 3. Then, in step S505, thecore network informs the mobile telephone 3 about the selected base time(i.e. TSFb parameter) by generating and sending (via the RAN(s) servingthe mobile telephone 3) an appropriately formatted Attach/RAU/TAU acceptmessage. This message informs the mobile telephone that the core network7 supports the extended DRX feature. Upon receipt of the message atS505, the mobile telephone 3 stores the received TSFb parameter in itsmemory 39.

If the current RAN that the mobile telephone 3 camps on also supportsthe extended DRX feature, the DRX module 45 calculates the start time ofthe SFb (hereafter referred to as STb) by working out the remaining timebetween the current time (within the current SFN) and the TSFb using theformula shown in FIG. 11I a. The DRX module 45 can also calculate thetiming of the active SFs and dormant SFs according to the formulaillustrated in FIG. 10b . However, if the mobile telephone's 3 currentRAN does not support the extended DRX feature it is not necessary forthe DRX module 45 to perform these calculations.

Next, when the core network 7 needs to initiate paging, it sends the Na,Nd and TSFb parameters to the RAN(s) serving this mobile telephone 3. Inorder to do so, the core network 7 generates and sends, at step S513, apaging request (in this example to RAN-A and RAN-B). When RAN-A, whichdoes not support the extended DRX feature, receives the message at S513,it ignores the included Na, Nd and TSFb parameters (i.e. withoutreturning any error message to the core network 7) as it is unable tointerpret them.

As shown generally at step S515A, RAN-A generates and sends one or morepaging messages to the mobile telephone 3 according to the normal DRXprocedure defined in the current 3GPP specifications. Since the mobiletelephone 3 knows (from the SI message at S501 a) that RAN-A does notsupport the extended DRX feature, it receives the paging messagescorrectly by following the existing (non-extended) DRX procedures forthis RAN-A.

On the other hand, when RAN-B (which supports the extended DRX feature)receives the message at S513, it calculates the STb according to themethod shown in FIG. 11a , and also calculates the timing of the activeSFs and dormant SFs according to the method shown in FIG. 10 b.

If the current system frame, i.e. when the paging request is received(at S513), is a dormant SF (according to the calculations in theprevious paragraph), the RAN-B delays sending of any paging messagesuntil the next active SF, as generally shown at S515 b. Then in the nextactive SF(s), the RAN-B generates and sends one or more paging messagesto the mobile telephone 3. The exact number and frequency of pagingmessages is implementation dependent. Since both the RAN-B and themobile telephone 3 follow the same timing of the extended DRX procedure,the mobile telephone 3 operates its transceiver 31 and is capable toreceive the paging messages correctly during the active SFs.

If necessary, the mobile telephone 3 can select another RAN (e.g.instead of RAN-A which does not support the extended DRX functionality)by monitoring SI messages broadcast by other RANs in its geographicalarea. For example, the mobile telephone can receive, at step S517, theSI message broadcast by RAN-C. The mobile telephone 3 can camp on RAN-C.In this case the mobile telephone 3 also needs to synchronise to the newRAN-C, and calculate the STb value and timing of active and dormant SFsfor RAN-C in a similar manner as described above for RAN-B.

This approach ensures that the mobile telephone 3 always remains in syncwith the radio access network it is camping on and thus improves theefficiency of delivery of paging messages whilst also reduces the mobiletelephone's 3 battery consumption.

Second Embodiment—DRX Cycle Synchronisation Using Time of LocationRegistration

FIG. 6 shows an example timing diagram illustrating a method performedby components of the communication system 1 when carrying out paging ofa mobile telephone 3 configured with an extended DRX cycle. Thisembodiment generally follows the first embodiment, however, instead ofthe core network selecting an arbitrary start time for the mobiletelephone's 3 extended DRX cycle, a request-response procedure iscarried out between the core network 7 and the RAN to derive a UEspecific start time for the extended DRX cycle.

Steps S601 a and S601 b generally correspond to the respective SIbroadcast messages at S501 a and S501 b described above with referenceto FIG. 5. However, the messages sent at S601 a (by RAN-A) and at S601 b(by RAN-B) do not carry the current time information for the given RAN.Alternatively, if the messages at steps S601 a/S601 b include thecurrent time information, in this embodiment the mobile telephone 3 canignore this information.

Step S603 generally corresponds to S503 of FIG. 5 and hence it will notbe described in detail. The message at S603 is used by the mobiletelephone 3 to inform the core network 7 about its DRX configuration andit also includes the Na and Nd parameters configured for the mobiletelephone 3.

However, in this embodiment, instead of responding to the request atS603, the core network 7 generates and sends, at step S605, anappropriately formatted setup message to the RAN on which the mobiletelephone 3 currently camps (as indicated in the preceding message). Thecore network 7 also includes in this setup message the appropriateAttach/RAU/TAU accept message (which includes an indication of the corenetwork's 7 capability to support the extended DRX feature) for themobile telephone 3. In case of E-UTRAN, the setup message to the RAN maycomprise, for example, an ‘Initial Setup Context Request’ message. Inthis case, the core network 7 also includes a time info requestparameter instructing the compatible RAN to return informationidentifying the time when the Attach/RAU/TAU accept message is sent tomobile telephone 3.

When sending the message setup at S605, the core network 7 provisionallystores the time of sending this message as ‘provisional’ start of theextended DRX cycle (provisional TSFb) for this mobile telephone 3.

Upon receipt of the setup message (e.g. Initial Setup Context Requestmessage) by the RAN including the Attach/RAU/TAU accept message for themobile telephone 3 and the time info request, the RAN generates andsends, at step S607, an RRC message (e.g. a ‘Connection Reconfiguration’message or other suitable message) instructing the mobile telephone 3 toconfigure its communication control module 43 for communication with thegiven RAN (in this case, RAN-B). This RRC message also includes theAttach/RAU/TAU accept message from the core network 7 and the indicationof the core network's 7 capability to support the extended DRX feature.The RAN-B also stores the time of sending the Attach/RAU/TAU acceptmessage to the mobile telephone 3 as the TSFb parameter to be used bythe network.

From the received Attach/RAU/TAU accept message, which includes theExtended DRX feature support indicator, the mobile telephone 3 candetermine that the core network 7 also supports the extended DRXfeature. Therefore, it stores the reception time of the Attach/RAU/TAUaccept message as the TSBb parameter to be used for the extended DRXcycle, and then it calculates the STb and timing of active and dormantSFs as described above. In step S609, the RAN-B returns the TSFbparameter to the core network 7 in a response to the preceding setupmessage (e.g. in an ‘Initial Setup Response’ message in case ofE-UTRAN). When the core network 7 receives the response to the setupmessage, it stores the TSFb parameter (and discards the previouslystored provisional TSFb parameter).

However, if the core network 7 does not receive the TSFb timeinformation (e.g. because the current RAN does not support the extendedDRX feature), the core network 7 will use the provisionally stored TSFbas the TSFb for this mobile telephone 3 and RAN. The remaining stepsS613 to S617 of the second embodiment generally correspond to steps S513to S517 of the first embodiment and hence their description is omitted.

Advantageously, in this embodiment the core network 7 can verify (usingthe request-response procedure at steps S605 and S609) which radioaccess networks support the extended DRX cycle functionality. Therefore,the core network 7 will be able to determine the expected scheduling ofpaging messages in each network and it does not have to repeat thepaging request (sent at S613) if the paging messages are delayed for theduration of dormant SFs in a RAN supporting the extended DRXfunctionality. However, if the mobile telephone 3 does not respond tothe paging request(s) within a predetermined time (e.g. due tounfavourable signal conditions or movement of the mobile telephone 3preventing it from receiving them), the core network 7 can repeat thepaging for this mobile telephone 3 (possibly over a larger geographicalarea, i.e. involving a larger number of base stations 5 than in case ofthe initial paging attempt).

Third Embodiment—Extended DRX Cycle without Ran Support

FIG. 7 shows an example timing diagram illustrating another methodperformed by components of the communication system 1 when carrying outpaging of a mobile telephone 3 configured with an extended DRX cycle.This embodiment generally follows the first embodiment, however, thecore network 7 provides support for the extended DRX operation withoutinvolving the RAN(s).

In this example, the mobile telephone 3 initially registers its currentlocation with a core network entity (e.g. the MME 9) by sending, at stepS703, an appropriately formatted NAS message, as explained above withreference to step S503 of FIG. 5. The NAS message (which may comprise anAttach/RAU/TAU Request) includes the mobile telephone's 3 Na and Ndparameters (i.e. the number of active and dormant SFs in its extendedDRX cycle) thereby informing the core network 7 about its capability forthe extended DRX cycle functionality.

When an entity in the core network 7 (e.g. the MME 9) receives themessage sent at S703 including the Na and Nd parameters, it stores theseparameters as the UE specific values of the extended DRX feature forthis mobile telephone 3.

Next, in step S705, the core network 7 generates and sends anappropriately formatted response (e.g. a NAS response such as anAttach/RAU/TAU accept message), and includes in this responseinformation indicating that it supports the extended DRX feature (e.g.an extended DRX feature support indicator TE or flag). The core network7 derives (as per FIG. 10b or FIG. 11a ) the scheduling of active anddormant SFs using the time of sending this response (i.e. S705:Attach/RAU/TAU accept message) as the STb.

When the mobile telephone 3 receives the response with the extended DRXfeature support indicator (at S705), it also schedules the active anddormant SFs for the current RAN and performs the extended DRX procedureaccordingly. However, the mobile telephone 3 also schedules extra activeSFs as described in detail with reference to FIG. 11c below.

When the core network 7 detects (at S711) a trigger for paging thismobile telephone 3 (and it determines that the current SF is a dormantSF for this mobile telephone 3), it waits until the next active SFbefore sending the paging request, in step S713, to the RAN serving themobile telephone 3.

Since in this embodiment the RAN is not required to be aware of theextended DRX feature in use, it simply sends the prescribed number ofpaging messages to the mobile telephone 3, according to the normal DRXprocedures, as generally shown at step S715. Since the core network 7does not request the RAN to carry out paging for the mobile telephone 3during any dormant SFs (only during active SFs), successful receipt ofthe paging messages by the mobile telephone 3 can be ensured.

When the mobile telephone 3 subsequently selects a new RAN to camp on(e.g. RAN-A instead of RAN-B), as generally shown at step S719, itmaintains its current scheduling of active and dormant SFs (that wasbased on the time of sending the NAS message at S703). Even though thecore network 7 is not aware of the cell re-selection by the mobiletelephone 3, since the scheduling of active and dormant SFs is notchanged, any further paging messages can be delivered to this mobiletelephone 3 in the same manner as before assuming that the core network7 requests paging of the mobile telephone 3 via each RAN under itscontrol. As illustrated in steps S721 to S725, after re-selection, themobile telephone 3 receives the paging messages via its new RAN-A.

Fourth Embodiment—Using Sequential System Frame Cycle Index

FIG. 8 shows an example timing diagram illustrating another methodperformed by components of the communication system 1 when carrying outpaging of a mobile telephone 3 configured with an extended DRX cycle.This embodiment generally follows the first embodiment, however, asequential system frame number is used to synchronise the extended DRXoperation between the RAN and the mobile telephone 3 instead of the RANspecific current time information.

In this embodiment, steps S801 a to S811 and step S817 generallycorrespond to steps S501 a to S511 and S517 of FIG. 5, respectively,thus detailed explanation of any identical features will be omitted. Inthis example, however, RAN-B which supports the extended DRX cyclefunctionality transmits (e.g. as part of the SI broadcast message atS801 b) a sequential number identifying the current SF (SF #) ratherthan an explicit indicator of its compatibility with the extended DRXcycle feature and current time information (as in step S501 b). This SFnumber informs the mobile telephone 3 that RAN-B is compatible withextended DRX cycles. As can be seen, RAN-B which does not support theextended DRX cycle feature does not include SF # in its SI broadcastmessage (S801 a).

Upon receipt of the NAS message (at S803) which includes the Na/Nd valuefor the mobile telephone 3, the core network 7 derives the scheduling ofactive and dormant SFs according to the procedures described withreference to FIG. 10 c.

In response to this, in step S805, the core network 7 provides anindication of its compatibility with the extended DRX feature (e.g.extended DRX feature support indicator) using an appropriately formattedNAS response (e.g. an Attach/RAU/TAU accept message) sent to the mobiletelephone 3.

Upon receipt of a paging request from the core network 7 (at S813) whichincludes the Na, Nd parameters and an identification of the mobiletelephone 3, such as an IMSI, each RAN performs paging of the mobiletelephone 3 according to its DRX capability.

Thus RAN-A (which does not support the extended DRX feature) sends theprescribed number of paging messages to the mobile telephone 3 accordingto the normal DRX procedures (in radio frames during which the mobiletelephone's 3 transceiver 31 is assumed to be active).

However, if RAN-B (which supports the extended DRX feature) receives thepaging request from the core network 7 during a dormant SF, it postponessending of any paging messages until the next active SF for this mobiletelephone 3. Of course, if RAN-B receives the paging request from thecore network 7 during an active SF, it sends the prescribed number ofpaging messages to the mobile telephone 3 without additional delay(according to the normal DRX procedures).

FIG. 12a (which is described in detail below) illustrates furtherdetails of this embodiment.

Configuring an Extended DRX Cycle Using an OMA DM Server

FIG. 9 illustrates a possible way of configuring the parameters relatedto the extended DRX cycle for a mobile telephone 3. In this example, asshown in step S900, an OMA DM server entity 12 is used to update (bycommunicating with the OMA DM module 47) the DRX configuration stored inthe memory 39 of the mobile telephone 3. This step may be performed atany time, whenever a change in the mobile telephone's 3 extended DRXcycle configuration is needed.

When the extended DRX functionality is turned on and/or when updatedparameters have been received by the mobile telephone 3, it can includethe current (updated) DRX parameters in a subsequent NAS request (atS903) to inform the core network 7 about the change in the mobiletelephone's 3 DRX configuration. Upon receipt of the message at S903(which may generally correspond to either one of messagesS503/S603/S703/S803 described above), the core network 7 (and possiblythe RAN as well) updates its operation in accordance with the newlyreceived configuration.

Accordingly, at least the following parameters can be configured for themobile telephone 3:

-   -   Na;    -   Nd; and    -   Extended DRX feature on/off.

If the number of active/dormant SFs (i.e. Na/Nd) is updated via the OMADM entity 12, the mobile telephone may advantageously notify the corenetwork about its new Na and/or Nd by generating and sending anappropriately formatted NAS message, e.g. an Attach/RAU/TAU requestmessage. This will in turn cause the core network 7 to also update theextended DRX functionality in place for this mobile telephone 3.

If the Extended DRX feature is switched off, the mobile telephone mayadvantageously notify the core network 7 about this by generating andsending an appropriately formatted NAS message, e.g. an Attach/RAU/TAUrequest message, without including the number of active/dormant SFs.This will in turn cause the core network 7 to also turn off the extendedDRX functionality for this mobile telephone 3 (although normal,non-extended DRX functionality may still be used).

Modifications and Alternatives

Detailed embodiments have been described above. As those skilled in theart will appreciate, a number of modifications and alternatives can bemade to the above embodiments whilst still benefiting from theinventions embodied therein.

FIG. 10a illustrates the general extended DRX cycle feature of the aboveembodiments applicable to the LTE frame structure for E-UTRAN.

In order to achieve a longer DRX cycle than the SF length, the one ormore consecutive active SFs and the one or more consecutive dormant SFsare scheduled periodically. Within any dormant SFs, the mobile telephoneis configured to turn off its receiver as the network does not send anypaging messages to this mobile telephone during dormant SFs. Withinactive SFs, however, normal DRX scheduling methods defined in thecurrent 3GPP specifications are applied.

Since the mobile telephone and the network need to share the same timingof active and dormant SFs, various methods for specifying the active SFsand the dormant SFs can be provided. As explained above, one possiblemethod involves using a so-called base SF (referred to as SFb) as thestarting SF for the periodic scheduling of the active SFs and dormantSFs. The SFb is specified by an absolute time (i.e. as an exact point intime). Another possible method includes assigning a sequential number(for example, from #0 to #1023) to each SF and informing this numberfrom the RAN to the mobile telephone, for example as part of theperiodic SI broadcast messages.

Advantageously, if the time of the SFb is decided and shared between themobile telephone and the network, both the mobile telephone and thenetwork are able to follow the same scheduling of active SFs and dormantSFs based on the number of active SFs (Na) and the number of dormant SFs(Nd) calculated from the SFb.

FIG. 10b illustrates an exemplary method for calculating the schedulingof active and dormant SFs in the case of E-UTRAN in accordance with theabove described embodiments.

FIG. 10c illustrates another exemplary method for calculating thescheduling of active and dormant SFs in which sequential numbers areassigned to each SF. In this case, the start of an active SF (SSFa) canbe calculated using the following equation:

SSFa(x)=IMSI mod(Na+Nd)+(Na+Nd)*x; where SSFa(x)<i

In this case, the active SFs are located from SSFa(x) to SSFa(x)+Na−1and the dormant SFs are located from SSFa(x)+Na to SSFa(x)+Nd−1.

FIG. 11a illustrates the calculation of STb by the mobile telephoneusing the current time and current SFN and the TSFb provided by the corenetwork, in accordance with the above described embodiments.

FIG. 11b illustrates an exemplary configuration of an extended DRX cyclein accordance with the above described embodiments. In this example, thevalue of Na is 2 and the value of Nd is 3. Thus SF numbers 0, 1, 5, 6(and so on) are active SFs and the remaining system frames are dormantSFs.

FIG. 11c illustrates a modification of the embodiment described withreference to FIG. 6. In this example, if the mobile telephone's currentRAN does not support the extended DRX feature (such as RAN-A), themobile telephone may use the time of sending the Attach/RAU/TAU requestmessage (at step s603) to provide additional active SFs (referred to as‘extra active SFs’) preceding the actual active SFs so that when themobile telephone subsequently selects another RAN which supportsextended DRX cycles (e.g. RAN-C) it will be able to receive pagingmessages without the need to re-register its location with the corenetwork. This is made possible because (as described above withreference to FIG. 6) the core network stores the provisional TSFb forthose RANs that do not support the extended DRX cycle (i.e. for RAN-A aswell). Therefore, the core network (which is not yet aware that themobile telephone is now camping on RAN-C instead of RAN-A) will expectdelivery of paging messages earlier than the active SFs in currentRAN-C—it can be seen in FIG. 6 that step S615 a (RAN-A) takes placebefore step S615 b (RAN-B and hence also RAN-C). The autonomousprovision of ‘extra active SFs’ by the mobile telephone thus allowsreceipt of paging messages irrespective of the RAN that the mobiletelephone currently camps on. In the particular example shown in FIG.11c , the value of Na is 2 and the value of Nd is 3, as in case of FIG.11b . In this case however SF numbers 0, 5, 10 (and so on) that areotherwise dormant SFs will act as additional (extra) active SFs when themobile telephone camps on a new RAN that supports extended DRX cycles.

FIG. 12a illustrates further details of the exemplary fourth embodimentdescribed above with reference to FIG. 8. In particular, FIG. 12aillustrates a possible way of scheduling active and dormant SFs by themobile telephone.

Since in the fourth embodiment the RAN is not necessarily aware of theextended DRX cycle being in use (or it might not support suchfunctionality at all) and the mobile telephone is not aware of the exacttime of sending the Attach/RAU/TAU accept message, the mobile telephoneis configured to schedule extra active SFs to compensate for the corenetwork's possibly different scheduling of the active and dormant SFs(resulting from the different start time of each extended DRX cycle usedby the core network and the mobile telephone).

Therefore, the mobile telephone schedules the active SFs by according tothe following steps:

1. Any SFs overlapping with the time period between the mobile telephonesending the Attach/RAU/TAU request message and the mobile telephonereceiving the Attach/RAU/TAU accept message (and any SFs correspondingto these SFs in each subsequent DRX cycle) are set as active SFs. In theexample shown in FIG. 12a , these are SFs no. 0, 5, 10, etc.

2. Any SFs overlapping with the time period calculated as ‘SF length×Na’from the receipt of the Attach/RAU/TAU accept message are also set asactive SFs (groups of SFs). In the example shown in FIG. 12a , these areSFs no. 1 & 2, 6 & 7, 11 & 12, etc.

3. Any SFs immediately following the last active SF of the above groupsof SFs are also set as active SFs. In this example, these are SFs no. 3,8, 13, etc.

Step 3 ensures that the RAN (which is not aware of the extended DRXfeature) is able to successfully deliver paging messages to the mobiletelephone even if the core network entity requests paging only at theend of an actual active SF (since the core network's start time of thefirst extended DRX cycle is based on the time of sending theAttach/RAU/TAU accept message, which is later than the start timeassumed by the mobile telephone, i.e. the time of sending theAttach/RAU/TAU request message).

FIG. 12b illustrates a modified extended DRX cycle that allows themobile telephone to monitor SI broadcast messages, which might carryimportant updates concerning the RAN(s) it currently camps on.

According to the current 3GPP specifications for UTRAN and E-UTRAN, whenthe radio access network changes (some of) its system information, itnotifies the UEs about this change by sending a ‘BCCH modification info’or a ‘systemInfoModification’ info via one or more paging messages. Thedetails of this notification are described in section 8.1.1.7 of 3GPPTS25.331 and section 5.2.1.3 of 3GPP TS36.331, the contents of which areincorporated herein by reference.

Therefore, it is important for the mobile telephone to receive any SIupdates without delay. However, if the extended DRX feature is active,the mobile telephone does not read the paging messages sent during anydormant SFs. Therefore, in some cases the mobile telephone cannot benotified of the system updates immediately if the network indicates suchupdates via paging messages.

In order to mitigate this problem, the last dormant SF of each extendedDRX cycle may be defined as a so-called wakeup SF. Advantageously, themobile telephone is able to read the necessary SI messages/updatesduring such wakeup SFs and read any paging messages in the next SF(which is an active SF).

According to a modification of this technique, wakeup SFs may also beused for carrying out signal measurements by the mobile telephone ratherthan for receiving paging/SI broadcast messages. In this case, themobile telephone disables (i.e. by turning off its receiver) not onlypaging but cell measurement functionalities as well. However, in anywakeup SF, the mobile telephone may perform the necessary signalmeasurements and SI message reading, and if necessary, it may performcell re-selection.

Various embodiments have been described in which the mobile telephoneprovides information about its DRX configuration to the core network bygenerating and sending a request upon connecting to the RAN. However, itwill be appreciated that such information about the mobile telephone'sDRX configuration might be provided to the core network periodically,even if the mobile telephone's serving RAN does not change. Further, itwill also be appreciated that the information about the mobiletelephone's DRX configuration might be provided to the core network upon(or immediately preceding) the mobile telephone's activation of the DRXfunctionality (e.g. upon receiving a new configuration from the OMA DMserver or upon user input).

Although in FIG. 5 to FIG. 8 it is shown that the mobile telephone andthe core network use the Attach/RAU/TAU requests and responses toexchange information relating to the extended DRX cycle. However, itwill be appreciated that other messages may also be used, for example, adedicated DRX configuration message or any existing NAS message in whichthe information relating to the extended DRX cycle can be included.

Although not shown in FIG. 5 to FIG. 8, if a RAN that supports theextended DRX feature is configured to send more than one pagingmessages, it might not be able to send all paging messages within thecurrent active SF (or set of consecutive active SFs). In this case, itwill be appreciated that the RAN might postpone the sending of anyremaining paging messages until the next active SF (or set ofconsecutive active SFs).

In the above embodiments, the mobile telephone is described to activateits transceiver, in any active SFs, according to normal DRX schedulingmethods defined in the current 3GPP specification for non-extended DRXcycles (i.e. DRX cycles that do not exceed the length of the systemframe). However, it will also be appreciated that instead or employing aDRX cycle the mobile telephone may employ a different power savingmethod in active system frames. It will also be appreciated that insteadof employing any power saving method, the mobile telephone may operateits receiver/transceiver for the whole duration of an active systemframe and to turn off its transceiver only in dormant system frames.

In the above embodiments, the mobile telephone is described to switchoff its receiver (and hence not listen for any paging messages) for theduration of each dormant SF. However, it will be also appreciated that,instead of turning off its receiver, the mobile telephone may employ adifferent DRX cycle (e.g. one having fewer active radio frames) than theDRX cycle it is using in active system frames or use a different powersaving feature than the one it is using in active system frames (ifany).

In the above embodiments, a mobile telephone based telecommunicationssystem was described. As those skilled in the art will appreciate, thesignalling techniques described in the present application can beemployed in other communications systems. Other communications nodes ordevices may include user devices such as, for example, personal digitalassistants, laptop computers, web browsers, etc. As those skilled in theart will appreciate, it is not essential that the above described systembe used for mobile communications devices. The system can be used in anetwork having one or more fixed computing devices as well as or insteadof the mobile communicating devices.

In the above description, the base station and the mobile telephone aredescribed, for ease of understanding, as having a number of discretemodules. Whilst these modules may be provided in this way for certainapplications, for example where an existing system has been modified toimplement the invention, in other applications, for example in systemsdesigned with the inventive features in mind from the outset, thesemodules may be built into the overall operating system or code and sothese modules may not be discernible as discrete entities. These modulesmay also be implemented in software, hardware, firmware or a mix ofthese.

Whilst the signalling messages described herein that include the DRXconfiguration related information are advantageous in terms ofsimplicity, ease of implementation and minimising the number of messagesrequired, this information may be sent in any of a number of differentways, e.g. in multiple messages. Moreover, instead of modifying thedescribed signalling messages, completely new messages may be generatedwhich include the measurement results.

In the embodiments described above, the mobile telephone and the basestation will include transceiver circuitry. Typically this circuitrywill be formed by dedicated hardware circuits. However, in someembodiments, part of the transceiver circuitry may be implemented assoftware run by the corresponding controller.

In the above embodiments, a number of software modules were described.As those skilled in the art will appreciate, the software modules may beprovided in compiled or un-compiled form and may be supplied to the basestation or the relay station as a signal over a computer network, or ona recording medium. Further, the functionality performed by part or allof this software may be performed using one or more dedicated hardwarecircuits. Various other modifications will be apparent to those skilledin the art and will not be described in further detail here.

Summary

A brief summary of various features of the above embodiments is givenbelow:

-   -   Active SF: during any active SF the UE is able to listen to        paging messages. Any RAN node (i.e. base station/eNB) that        supports the extended DRX feature is able to page the UE during        active SFs as per the normal DRX scheduling methods defined in        the current 3GPP specifications. This ensures that backwards        compatibility can be maintained.    -   Dormant SF: During dormant SFs, the UE can conserve its battery        power by switching off its receiver. The UE does not need to        listen to paging messages during such dormant SFs since the        network does not perform paging for this UE during any of the        dormant SFs.    -   Wake-up SF: It is possible to use the last dormant SF of the        extended DRX cycle as a Wake-up SF, allowing the UE to carry out        reading of SI broadcast and measurements during such Wake-up        SFs. This beneficially allows the UE to start listening to the        paging messages as soon as it gets into the first active SF (of        the next extended DRX cycle) without missing any network        updates, especially if such updates are transmitted via paging        messages during dormant SFs of the UE. This could be especially        beneficial in e.g. a high mobility environment in which it would        otherwise take relatively longer for the UE before it can start        listening to paging messages.    -   Extended DRX feature support indication by RAN in the System        Information: RAN can beneficially broadcast its Extended DRX        feature support indicator in an SI message. The presence (or        absence) of this indicator informs the UE whether or not the RAN        node (i.e. eNodeB or RNC) supports the Extended DRX feature.    -   Extended DRX feature support indication from the core network in        the Attach/RAU/TAU accept message: An entity in the core network        (e.g. MME, SGSN, or MSC) is configured to include the extended        DRX feature support indicator in the Attach/RAU/TAU accept        message sent to the UE. This indicator informs the UE whether or        not the core network supports the extended DRX feature.    -   Dormant SF and Active SF negotiation between the UE and the core        network: The UE can request the extended DRX mode by sending to        the core network the number (i.e. 1 to ‘n’) of active SFs and        the number (i.e. 1 to ‘m’) of dormant SFs in an Attach/RAU/TAU        update request or another suitable NAS message. The core network        stores the numbers for dormant and active SFs (and possibly        their pattern) as UE specific information to be used for the        extended DRX feature.    -   Basing SF (SFb): This parameter specifies the starting SF for        the periodic scheduling of the active and dormant SFs of a given        extended DRX cycle. It may be defined as the time for SFb (in        which case it is referred to as TSFb), e.g. as an absolute time        in the format of YY-MM-DD HH:MM:SS.xx (e.g. with a minimum unit        being 10 ms which is the length of one radio frame). The        particular SF which includes the TSFb is regarded as the SFb.        For example, the core network can define/set the TSFb to the        time when it receives the Attach/RAU/TAU request message, to the        time when it sends the corresponding Attach/RAU/TAU accept        message, or to any past/future time.    -   Extended DRX configuration: An Extended DRX capable UE can be        configured for a specific extended DRX cycle by the OMA DM using        OTA or NAS signalling or using any configuration method suitable        to inform the UE about the required number of dormant and active        SFs in the extended DRX cycle.    -   Sequential numbering of the current SF broadcast in the System        Information: If the RAN supports the extended DRX feature, it        broadcasts the sequential number (i.e. 0 to ‘n’) of the current        SF in an SI message. The RAN assigns a sequential number to each        SF and the assigned number is broadcast in a SI message during        each SF. Using this sequential number, the RAN and the UE can        schedule the active and dormant SFs without having to define a        starting SF.

The above-mentioned processing may be executed by a computer. Also, itis possible to provide a computer program which causes a programmablecomputer device to execute the above-mentioned processing. The programcan be stored and provided to a computer using any type ofnon-transitory computer readable media. Non-transitory computer readablemedia include any type of tangible storage media. Examples ofnon-transitory computer readable media include magnetic storage media(such as floppy disks, magnetic tapes, hard disk drives, etc.), opticalmagnetic storage media (e.g. magneto-optical disks), CD-ROM, CD-R,CD-R/W, and semiconductor memories (such as mask ROM, PROM (ProgrammableROM), EPROM (Erasable PROM), flash ROM, RAM (Random Access Memory),etc.). The software modules may be provided to a computer using any typeof transitory computer readable media. Examples of transitory computerreadable media include electric signals, optical signals, andelectromagnetic waves. Transitory computer readable media can providethe software modules to a computer via a wired communication line (e.g.electric wires, and optical fibers) or a wireless communication line.

This application is based upon and claims the benefit of priority fromUnited Kingdom Patent Application No. 1308572.5, filed on May 13, 2013,the disclosure of which is incorporated herein in its entirely byreference.

REFERENCE SIGNS LIST

-   1 MOBILE TELECOMMUNICATION SYSTEM-   3 MOBILE TELEPHONE-   5 BASE STATION-   7 CORE NETWORK-   9 MOBILITY MANAGEMENT ENTITY (MME)-   11 HOME SUBSCRIBER SERVER (HSS)-   12 OPEN MOBILE ALLIANCE (OMA) DEVICE MANAGEMENT (DM) SERVER-   13 FRAME-   15 SUB-FRAME-   17 SLOT-   19 OFDM SYMBOL-   21 PRB-   31 TRANSCEIVER CIRCUIT-   33 ANTENNA-   35 USER INTERFACE-   37 CONTROLLER-   39 MEMORY-   41 OPERATING SYSTEM-   43 COMMUNICATIONS CONTROL MODULE-   45 DISCONTINUOUS RECEPTION MODULE-   47 OPEN MOBILE ALLIANCE DEVICE MANAGEMENT MODULE-   51 TRANSCEIVER CIRCUIT-   53 ANTENNA-   55 NETWORK INTERFACE-   57 CONTROLLER-   59 MEMORY-   61 OPERATING SYSTEM-   63 COMMUNICATIONS CONTROL MODULE-   65 DISCONTINUOUS TRANSMISSION MODULE-   67 PAGING MODULE

1-62. (canceled)
 63. User equipment (UE) comprising: a transceiverconfigured to receive, from a core network entity of a communicationsystem, an Attach Accept message or a Routing Area Update (RAU) Acceptmessage upon a successful Attach or RAU procedure; and a processorconfigured to synchronize an extended Discontinuous Reception (DRX)cycle to a time of receipt, by the transceiver, of the Attach Accept orthe RAU Accept message.
 64. The UE according to claim 63, wherein theprocessor is configured to maintain said synchronized extended DRX cycleregardless of a Radio Resource Control (RRC) mode of the UE.
 65. The UEaccording to claim 63, wherein the received Attach Accept or RAU Acceptmessage includes at least one extended DRX parameter, and wherein theprocessor is configured to determine a start of an extended DRX cyclebased on the at least one extended DRX parameter such that the start ofthe extended DRX cycle is determined to coincide with the receipt, bythe transceiver, of the Attach Accept or the RAU Accept message thatincludes said at least one extended DRX parameter.
 66. The UE accordingto claim 63, wherein the processor is configured to start the extendedDRX cycle upon receipt of the Attach Accept or the RAU Accept message.67. The UE according to claim 63, wherein the processor is configured tocontrol the transceiver to monitor for paging messages or systeminformation messages in accordance with the extended DRX cycle.
 68. Acore network entity comprising: a transceiver configured to send, to auser equipment (UE), an Attach Accept message or a Routing Area Update(RAU) Accept message upon a successful Attach or RAU procedure; and aprocessor configured to synchronize an extended Discontinuous Reception(DRX) cycle to a time of sending the Attach Accept or the RAU Acceptmessage.
 69. The core network entity according to claim 68, wherein theprocessor is configured to maintain said synchronized extended DRX cycleregardless of a Radio Resource Control (RRC) mode of the UE.
 70. Thecore network entity according to claim 68, wherein the Attach Accept orRAU Accept message includes at least one extended DRX parameter, andwherein the processor is configured to determine a start of an extendedDRX cycle based on the at least one extended DRX parameter such that thestart of the extended DRX cycle is determined to coincide with thesending, by the transceiver, of the Attach Accept or the RAU Acceptmessage that includes said at least one extended DRX parameter.
 71. Thecore network entity according to claim 68, wherein the processor isconfigured to control the transceiver to transmit, to the RAN, messagesthat enable the RAN to transmit to the UE paging messages or systeminformation messages in accordance with the extended DRX cycle.
 72. Amethod performed by user equipment (UE), the method comprising:receiving, from a core network entity of a communication system, anAttach Accept message or a Routing Area Update (RAU) Accept message upona successful Attach or RAU procedure; and synchronizing an extendedDiscontinuous Reception (DRX) cycle to a time of receipt of the AttachAccept or the RAU Accept message.
 73. A method performed by a corenetwork entity of a communication system, the method comprising:sending, to a user equipment (UE), an Attach Accept message or a RoutingArea Update (RAU) Accept message upon a successful Attach or RAUprocedure; and synchronizing an extended Discontinuous Reception (DRX)cycle to a time of sending the Attach Accept or the RAU Accept message.74. A non-transitory computer-readable medium comprising computerimplementable instructions that, when executed by a programmablecommunication device, the programmable communication device to perform amethod according to claim
 72. 75. A non-transitory computer-readablemedium comprising computer implementable instructions that, whenexecuted by a programmable communication device, the programmablecommunication device to perform a method according to claim 73.